Global Navigation Satellite Systems (GNSS) comprise several satellite based positioning systems such as, for example, Global Positioning System (GPS), GLObal NAvigation Satellite System (GLONASS), Galileo, etc. Global Navigation Satellite Systems work similarly, typically using triangulation of signals from more than one satellite to estimate the position. Various estimation algorithms may provide accuracy within a few meters, or much higher precision for advanced algorithms.
A wireless communication device can obtain a position indication via GNSS. For example, GNSS-based positioning is often used for navigation, routing directions, and tracking of movement, e.g. of a vehicle. In some applications, an integrated GNSS tracking device may estimate the current position of the device and report it to a control center for monitoring or analysis, which may be in real-time or may be based on recorded data.
Even though they may be accurate in terms of position, GNSS systems suffer from the weakness that the signal may be unreliable. Typically, nothing guarantees the authenticity of a received GNSS signal. Hence, it is possible to significantly manipulate the position estimated by a wireless communication device, for example by using an interfering GNSS signal. Furthermore, a fraudulent or hijacked wireless communication device may, itself, manipulate the position after estimation and before reporting. Similar problems may arise for other types of positioning than those based on GNSS.
Thus, there is a need to determine whether a position estimate is valid. US 2010/0287038 A1 discloses a road toll system comprising a vehicle-mounted unit having a satellite navigation receiver implementing a position tracking function. The system also comprises a sensor for detecting a local vehicle condition dependent on the absolute position of the vehicle. The authenticity of the position tracking information is validated using the sensor information. The sensor may be for detecting mobile telephony signals and may comprise a mobile telephony receiver implementing a position tracking function. The vehicle communicates with a back-end server. However, the back-end server must rely on a smart card in the vehicle performing the validation. Thus, if the smart card is fraudulent, hijacked or otherwise tampered with, the back-end server can still not trust that the position tracking information is valid.
Hence, there is a need for improved validation of position indications.